Abstract： In order to better understand the influence of composition materials and pore structure of C50 concrete, the tests by using mercury intrusion method, rapid freeze-thawing method, American coulometric method, dry-wet cycling corrosion method, etc. have been done for investigating the influence of adding compound mineral admixture and air entraining agent, alonely or together, on the pore structure and durability of C50 concrete, then the influence law was analysed. The test results show that, for C50 concrete, the compound mineral admixture has little effect on porosity, but the proportion of harmless pores to the whole pores is increased, while the proportion of slightly harmful, harmful and more harmful pores are decreased, which will favorablely influence on impermeability and corrosion resistance of concrete, however, the effection on forst resistance is not obvious. When adding air entraining agent, the porosity of closed pores in concrete is increased, which has favorable influence on frost resistance, but the impermeability and corrosion resistance will be decreased since the quantity of opening pores (﹥20nm) are increased. When adding both , although the porosity of concrete is increased, the pore size distribution of concrete will become more reasonable than alonely adding air-entraining agent. And this is favorable for impermeability, frost resistance and corrosion resistance of concrete.